Grate



July 9, 1946.

C. V. CARROLL GRATE Filed Aug. '7, 1944 n E. Nm N .VNWLL Patented July 9, i946VV 2,403,737 `-GRATE VV,Charles Carroll, -Minneapolis,A Minn., assigner to. Wm. Bros.l Boiler & Manufacturing Co., Minneapolis, Minn., a corporation of Minne- Sota Application August7, 1944, SerialNo. 548,398

9 Claims. (Cl.V 1261-163) Y 4This `invention relates to the design of lgrate -surfaces'used for supporting and/or furnishing air to a solid fuel bed for combustion on the grate surface, the-grate surface design being applicable `to any type `of grate structure such as a shaker grate, dumping grate, chain grate .or rotating grate. It is known that for efficient combustion fof solid fuels without an undue excess air loss it is necessary to supply air uniformly to the under side of the solid fuel bed. This function of uniform air-supply has been accomplished in the past, with. only parta-l success. ofvthis invention vto provide a more satisfactory design `-of gratesurface capable of delivering air uniformly to `the under sideof a solid fuel bed. I havefoundthat foreflicient combustion of thin -solid fuel beds particularly, itis desirable tosupla ply the air ina manner so as to produce. a swirl- Ying action. and divergent air .flow so that the solid fuel bed is vprovided with combustion air uniformly throughout'its, entire'Y area.

It. is an object -of ther vinvention Yto provide a grate surface of improved design capablerof accomplishing these functions and yet of a design such that grate elements may be replaced easily Without disturbing other elements. k'It is ak further 'objectv of the invention to provide an exceedingly rugged grate element capable of withstanding roughusage and extreme temperature variations. It is a.v further and especial object of the invention to provide an improved grate sur.-

face capable Yof delivering air flow uniformly in a plurality of divergent swirling paths to a solid [fuel bed without at the same time presenting any straight-through vertical passages over the grate area, and to provide a grate lsurface wherein the combustionv air supply is .metered-through orices and then expanded so as to reduce the air lvelocity and' thereby reduce fly-ash difliculties.

It is also an object of the invention to provide a grate surface of non-sifting character.U It is a 'further object of the invention to provide an improved design of grate surfaces capable of being manufactured at 10W cost without the necessity of coring or other expensive molding procedures.

Other and further objects of the inventionare those inherent in the apparatus herein illustrated, described` and claimed. y

The invention is illustrated. with reference to the drawing whereinV Figure 1 is a top plan view of ka single grate elemente; i

Figure 2 is a side elevational view of a grate element illustrated in .Figure l;

It isan object Figure 3 isa topplan view of a grate element `and a portion of two Vadjacent grate elements,

one on each side; f i

Figure lis an enlarged fragmentary sectional View taken along the lines 4-4 of Figure 2; Figure 5 lis an enlarged fragmentary isometric View of a grate element of Figure 1'; and

Figure 6 is a fragmentary sectional view of .adjacent portions of two grate elements.

Thegrate surface vof the present invent-ion'is illustrated -as applied to `a shaker .or dumping type of grate but it will .be understood to be applicable `to-other types of grates. .Referring to the drawing there is illustratedY a grate bar generally designated I-IJl of the-type used in hand or stoker fired, Vstationary or -movable lboilers tical.` `junction of the top surface IS- and the side surface I9 there are provided a plurality of notches wherein the grate `bars are mounting upon a carrier bar generally designated-I I which is trun- `nioned about pivots t2 so 'as to allow the carrier barY IIand the Igratebar IU thereon toY be rotated in the direction of arrow I3 for grate shaking anddumping operation. yThe re surface of the grate bar |70, to thedesign of `which the .invention is particularlyA directed, is illustrated generally at l5 and maybe considered as `consisting of a thickened head portion having a top surface I-S` and side surfaces I:8 and I9, the side surfaces being parallel with each other and ver- Along the upper corner formed at the 2B of identical configuration and along the junction ofthe top I6l and-side surface I8, there are a plurality of notches V2|, likewise identical with those at 29. The notchesk 20 on thefsidev surface I9 .are staggered with relation to the notches 2.I on -the side surface I8, as shown in the drawing. The intervening spaces between the notchesv 20 and 2i are chamfered off slightly, as illustrated at 22 and 2.3, though the chamfering is not so extensive as toreach the level of the notches 20 and 2|. notches 20 and 2|y are approximately equal in width to the width `of the notches and each intervening space is providedl with an air chute in'- taglio recess 24 formed into'the side Wall.` Thus,

as shown in Figure 5, the side wall I9 is provided with air chutes 24 having parallel walls 24a and 24h and a uniform intaglio depth illustrated by the bracket 24e.

The air chutes 24 terminate at the level of line 25-25, illustrated by the dimension Aof Figures 2 and 5, it being-noted that the air chute is tapered out as illustrated at :24e so as to causethe air moving upwardly in the-air chute to be forced out The intervening spaces between the 'on the grate. -notches 2Q and 2l reduce the velocity of the air walls 2 la and 2 Ib of the notches 2| are preferably'l not quite vertical and are filleted into the surfaces 20c and 2 Ic of their corresponding notches.

Referring to Figure 1, it will be observed that the notches 20 terminate at a line 30-30 separated by the dimension E from the centerline of the grate bar, the notches 2| being similarly terminated at the line 3|-3|, likewise separated from the center line by the dimension F. Dimensions E and F are preferably equal.

Referring to Figure 3 the grate bar 10 is mounted with its side surf aces in contact with the side surfaces of grate bars Illf and I". Thus the surface I8 of grate bar IU is in contact with the surface I9' of grate bar Ill and the surface |,9 of grate bar l0 is in contact with Ythe surface I8" of grate bar I0. Since the air chutes 24 and the notches 20 and 2| on opposite sides of each grate bar are staggered with respect to each other, the mounting of a plurality of grate bars I0, l0 and l0 side by side serves to locate the notches 20 and 2| of one grate bar, for exampler I0, opposite the air chute of the adjacent grate bars I0 and I0". Referring to Figure 6 it will be observed that the air chute 24 of grate bar IB is thus adjacent the notch 2|" of the grate bar HJ, and since the air chute 24 extends upward to a dimension A, which is greater than the lowermostedge of the air chute 2|", the air chute and notch thus overlap slightly, and air may accordingly move upwardly, as illustrated by the arrows 32 of Figure 4. The air is deflected outwardly by the outwardly slanted surface at the upper part of the air chute 24 and upon reaching the notch 2| which also converges upwardly, the air is distributed to a larger area of the grate than is represented merely by the cross section of the air chute 24. It will thus be observed that notches 24 and 24" serve as metering orifices through which the volume of combustion air may be carefully'controlled by suitable regulation of the draft At the same time, the expanding before it reaches the fuel bed and consequently diminishes fly-ash trouble.

Referring again to Figure 6, it will be observed that air chutes 24" of grate bar I0" lie opposite notches 2|-2I of grate bar l0, and Serve to deliver air to them in the same way as air chutes 24 delivei air to notches 2|. It may also be noted that there is no vertical passage through the grate assembly of` a plurality of grate bars. See Figure 4.

The staggered 'relationship of the notches on -4 more uniform distribution of combustion air in accordance with the design here presented.

In the grate design of the present invention the side of each grate lies in contact with the side of the adjacent grates, the air passage portion excepted. No space is therefore available` through which sifting may occur, fortheupward draft and bent configuration of the air passages (see Figure .4) serves to prevent downward movement of ash 104 at these places. Sifting is therefore substantially i eliminated.

As there are no interior areas in the grate design the entire grate surface may be cast by opposite sides of the grate cause a definite swirling action 0f the air, as illustrated by the arrows 35 in Figure 3, thus causing the air to be distributed over a large portion of the solid fuel bed immediately in contact with the grate surface. It has been observed that with a grate surface of the design herein illustrated that there is a uniform distribution of air in a solid fuel bed, even Where the fuel bed has a depth of as little as one inch, whereas grate surfaces of prior design showed definite points of intense burning with a fuel bed of corresponding depth.- This proves the ordinary green sand molding and does not require any coring.

It is to be understood that the grate surface of the present invention is applicable to grate bars, chain grates, dumping or rocker grates and other forms of grates wherein air is delivered to the solid fuel bed. The form of support for the grate bar is adapted to the mechanical under-construction of the grate, and to the fuel and air feeding systems employed.- Y

As many apparently widely different embodiments of this invention may be made withoutdeparting from the spirit and scope thereof, it is to be lunderstood that I do not limit myself to the specific embodiments herein except as defined by the appended claims.

`Whatl I claim is:

1. A grate bar having a head portion composed of topl and bottomY surfaces and parallel flat side surfacesv forming the extreme lateral surfaces of the bar, said surfaces being spaced apart a distance at least equal to the width dimensionof the bar, the edges at the junction of the top land side surfaces being inwardly notched at evenly spaced intervals along each side, air-passage grooves in said sides, said grooves extending only part way up the side from the bottom of the side surfaces, each said air-passage groove being located in the side surface spaces between the notches, and a downwardly extending support below said head portion.

2. A grate bar having a head portion composed of top and bottom surfaces and parallel flat side surfaces forming the extreme lateral surfaces of the bar, said surfaces being spaced apart a distance equal to the width dimension of the bar, the edges at the junction of the top and side surfaces being inwardly notched atevenly spaced intervals along each side, the notches along one Iof the flat sides being staggered with respect to the notches along the opposite side, airrpassage grooves in the sides, said grooves extending only part way up the side from the bottom of the side surfaces, each said air-passage groove being an indentation located in the side surface in the spaces between the notches, and a downwardly extending support below said head portion.

3. A grate bar having a head portion bounded by a top surface and parallel nat side surfaces, said side surfaces forming the extreme lateral surfaces of the bar, said surfaces being spaced apart a distance at least equal to the Width dirnension of the bar, the edges formed at the junction of the top and side surfaces being inwardly notched at regularly lspaced intervals along each side, the notches along one side being staggered with respect to the notches'on the other side, the surface of each said notch extending along an angularly disposed plane from near its bottom at the junction with the side surface in which it is located to near the middle of the top surface, said notches'being of increased width from bottom to top, and air passage grooves in the sides, said grooves being recessed into the side surfaces and reaching only part way up the side from the bottom of the side surfaces to a position above the bottom of the notch, each said air-passage groove being located in the side surface between the notches.,

4. The apparatus of claim 3 further characterized in that the air-passage grooves have Ya width in the direction along the side of the grate bar, approximately equal to the bottom width of the notches.

5. A grate bar of the type set forth in claim 3 further characterized in that the junction of the top and side surfaces is slightly charnfered between notches.

6. A grate surface comprising a carrier support and a plurality of grate bars, the fire element of each grate bar being composed of a solid member having a flat top surface and parallel flat vertical side surfaces, said side surfaces each including at continuous similarly shaped areas extending from one end of the grate bar to the other end, said areas each being a uniform distance from a vertical central -plane through the bar, the opposite edges formed by the junction of said top and both side surfaces being notched at regular intervals, the width of notches and intervening spaces being approximately equal, the notches along one side being staggered so as tobe opposite the spaces on the other side, air-chute recesses v indented into the side walls and extending only lpart way up the sidewall from the lower edge of the side wall to a level above the lowermost part of the notches, said air-chute recesses being in the intervening spaces between the notches on each side, said grate bars being mounted side by side on the carrier support with the side surface of adjacent bars in contact so as to locate the airchute recesses of one bar with the upper part of each air chute overlapping the lower part of the corresponding notchesof adj acent grate bars, and

with the flat continuous side area of one bar in-y contact with the similar area of the adjacent bar.

7. A grate bar wherein the fire element is composed Of a solid member havin-g a iiat top surtersection near but spaced above the lower edge of the side wall, said notches being of increasing width from bottom to top and terminated in face and parallel flat vertica1 side surfaces, said n line of intersection on `the top surface, said line of intersection being between the centerline of the grate bar and the side surface, air-chute recesses indented into each of the side walls, each said recess extending only part way up the sidewall from the lower edge of the side Wall and tapered out and terminated at a level above the line of intersection of the notch near the lower edge of the side wall, said air-chute recesses being in the intervening spaces between the notches on each side.

8. A grate bar of the type set forth in claim I further characterized in that the edges between the notches, formed by the junction of the top and side surfaces, is chamfered slightly.

9. A grate surface comprising a carrier support and a plurality of grate bars, the re element of each grate bar being composed of a solid member having a, flat top surface and parallel nat vertical side surfaces, said side surfaces each including flat continuous similarly shaped areas extending from lone end of the grate bar to the other end, said areas each being a uniform distance from a vertical central plane through the bar, the opposite edges formed by the junction of said top and both side surfaces being notched at regular intervals, the width of notches and intervening spaces being approximately equal, the notches along one side being staggered so as to be opposite the spaces on the other side, each said notch being a at chamfered surface extending from a line of intersection near, but spaced above, the lower edge of the side wall, said notches being of increasing Width from bottom to top and terminated in line of intersection on the top surface, said line of intersection being between the center line of the grate bar and the side surface, air-chute recesses indented into the flat surface of each of the side walls, each said recess extending only part way up the sidewall from the lower edge of the side wall and upwardly, being then tapered out and terminated at a level above the line of intersection of the notch near the lower edge of the side wall, said air-chute recesses being in the intervening spaces between the notches on each side, said grate bars being mounted side by side on the carrier support with the side surfaces of adjacentbars in contact so as to locate the air-chute recesses at one bar with rthe upper part of each air chute lapping the lower part. of the corresponding notches of adjacent grate bars, and with the flat continuous side area of one bar in contact with the similar area of the adjacent bar.

CHARLES V. CARROLL. 

